...also known as the publishing houses.
I've been a college student for almost ten years now - yeah, I know, I am a perpetual student - nothing wrong with that! Anyway, I have gone through almost three degrees now, and one thing is constant: textbooks are expensive! When I was an undergrad, I was young and stupid and bough everything at the college bookstore (and paid premium for it!). Now I do my homework beforehand, and I get my books online. The college bookstore (effollet.com) does not provide me with an ISBN number, because obviously people can go elsewhere if they know the ISBN! Here is a comparison for a book (for a class that I am not taking, but I took in the past)

Book: Operations Management
ISBN: 0131-69739-0
Authors: Larry P. Ritzman, Manoj K. Malhotra, Lee J. Krajewski

Prices on effollet (and in the college bookstore:
New: $162.00
Used: 121.50

Holly mother!!!

OK... now lets look on amazon, just in case we get a better deal:
New: $125.01
"New & Used": $68

OK better...but let's look on addall.com
Lowest Price: $30
but since it's only one, there are a couple that cost $50.

All I can say is WTF?!?!?! Why do college students accept this horrible gouging?
If someone can sell the book used for $50-68, why would you buy it used at the college book store for essentially double the price?
Why would you pay three times the price to get it new at list price? The textbook industry is despicable. We should be promoting knowledge, not inhibiting it by pricing textbooks so high!